Method of and apparatus for ligating orthodontic appliances

ABSTRACT

A ligature for securing an orthodontic bracket to an orthodontic archwire is formed from nylon and comprises a thin, elongate member having sufficient tensile strength to withstand orthodontic forces. A locking member receives the ligature therethrough and prevents disengagement of the ligature from an orthodontic bracket and an orthodontic archwire following installation. In one embodiment the ligature has locking teeth at one end and a locking member at the other end for cooperation with the locking teeth to prevent disengagement of the ligature. In another embodiment the ligature has locking teeth at both ends which engage one another and a locking tube to prevent disengagement of the ligature. In another embodiment the locking member is initially open and is closable to secure the ligature therein, thereby preventing disengagement of the ligature from an orthodontic bracket and an orthodontic archwire following installation.

This application is a continuation of Ser. No. 09/584,649, filed May 31,2000, now U.S. Pat. No. 6,203,318, which is a continuation of Ser. No.09/398,673 filed Sep. 17, 1999, now U.S. Pat. No. 6,071,120.

TECHNICAL FIELD

This invention relates generally to ligation techniques useful in the 3of othodontia, and more particularly to a method of and apparatus forligating orthodontic brackets to orthodontic archwires which is botheasy and economical to use, while at the same time providing comfort topatients.

BACKGROUND AND SUMMARY OF THE INVENTION

Although the practice of orthodontics can be traced back at least to thetime of the Egyptian mummies, modern development in the art began in the1920's when Dr. Edward Angle developed the first edgewise bracket. Sucha bracket is for the purpose of connecting an orthodontic archwire to atooth, as opposed to simply wrapping wires around the tooth and ligatingto an activating archwire as had been the practice previously. Later onthe so-called twin bracket to apply a greater rotating and torquingforce to the tooth. Still later developments included the Lewis gullwing bracket, the Steiner spring wing bracket, and the Lang stiff wingwhich incorporated a hole for ligating to rotate the booth.

Brackets for orthodontic use were originally had made from gold. In thelate 1930's brackets machined from stainless steel were introduced.Stainless steel is generally satisfactory as an orthodontic bracketmaterial, but presents numerous problems. First, it has traditionallybeen necessary to individually machine each bracket. This is costly, andalso results in highly angular edge surfaces which are veryuncomfortable for the patient. Another difficulty involved thedistinctive appearance of stainless steel, which many patients findobjectionable.

In an attempt to overcome the foregoing and other difficulties, plasticorthodontic brackets were introduced. Plastic brackets can be fabricatedso as to eliminate the angular edges of machined stainless steelbrackets, and are therefore more comfortable for the patient. It is alsopossible to make plastic brackets in almost any desired color, includinghighly transparent brackets. It has been found in practice, however,that the use of polycarbonate plastic orthodontic brackets presents adifferent set of problems. First, plastic brackets are too weak towithstand desired torquing stresses, so that breakage and failure arenot uncommon. Second, in the environment of the mouth, plasticorthodontic brackets tend to rapidly discolor due to stains caused byvarious foods, tobacco, and beverages such as tea and coffee, etc.

The foregoing problems relating to the use of stainless steel andplastic brackets are overcome by the use of ceramic orthodontic bracketswhich were introduced by Dr. James M. Reynolds in the 1970's. Ceramicbrackets do not have angular edges of the type associated with stainlesssteel brackets, and are therefore very comfortable in use. Ceramicbrackets are very strong and fully capable of withstanding the forcesthat are applied during orthodontic procedures. Also, ceramic bracketsdo not discolor in use, and therefore overcome the problems associatedwith plastic brackets. Ceramic brackets can be highly translucent sothat the color of the underlying tooth is observed through the bracketmaterial, and in such instances ceramic brackets are nearly invisible tothe eye.

Regardless of the particular material selected for the manufacture oforthodontic brackets, it is necessary to ligate or tie the bracket to anarchwire extending through an archwire slot formed in the bracket. Bymeans of appropriate and proper ligation, force is applied from thearchwire to the bracket and in turn from the bracket to the tooth uponwhich the bracket is mounted. Such force eventually leads to therepositioning of the tooth to the desired orientation.

Orthodontic ligation has typically been accomplished utilizing stainlesssteel wire. Notwithstanding its widespread use, the use of stainlesssteel wire to ligate orthodontic brackets to archwires results inserious difficulties. First, stainless steel wires almost universallyexhibit sharp ends which cause significant patient discomfort. Second,stainless steel, even in the form of small diameter wires, is highlyvisible in the mouth, which means that the use of stainless steelligatures substantially reduces the aesthetic benefits deriving from theuse of translucent ceramic brackets.

In order to overcome the foregoing difficulties with stainless steelligatures, plastic O-rings have been used to ligate orthodontic bracketsto archwires. U.S. Pat. No. 4,038,753, granted to Klein on Aug. 2, 1977,discloses such a plastic O-ring ligature. U. S. Patent No. 4,217,686,granted to Dragan on Aug. 18, 1980, discloses a ligator useful inconjunction with plastic O-rings to ligate orthodontic brackets toarchwires.

Although overcoming the difficulties long since associated withstainless steel ligatures, the use of plastic O-rings to effectorthodontic ligation present its own set of problems. First, theinjection molding process which is utilized in the manufacture ofplastic O-rings is incapable of maintaining tolerances sufficiently toassure that O-ring ligatures that are nominally the same size can berelied upon to apply the same force. Additionally, and similarly toplastic orthodontic brackets, plastic O-rings tend to stain and discolorwhen used within the mouth of a patient.

The present invention comprises a method of and apparatus fororthodontic ligation which overcomes the foregoing and otherdifficulties long since associated with the prior art. In accordancewith a first embodiment of the invention, an orthodontic ligature isformed from a material having a high tensile strength which does notstain or discolor when employed within the mouth of a patient. Theligature has sufficient length to be deployed around the tie wings of anorthodontic bracket and over an archwire extending through the archwireslot of the bracket. One end of the ligature comprises and insertion endand is provided with a series of locking teeth each having a lockingsurface facing away from the insertion end of the ligature. The oppositeend of the ligature comprises a locking end and included a lockingaperture adapted to receive the insertion end of the ligature and toengage the locking surfaces of the teeth thereof to preventdisengagement of the ligature after installation.

In accordance with other aspects of the invention, the ligature isformed from nylon. This is advantageous in that nylon does not discoloror stain when utilized within the human mouth. Also, nylon can bemanufactured so as to be highly translucent or the ligature of thepresent invention can be provided in a plurality of colors, if desired.Another advantage is that nylon is a relatively low-friction material ascompared to prior art orthodontic materials.

In accordance with still other aspects of the first embodiment. theligature comprises an elongate strip having a series of locking teeth atthe insertion end and having a locking tube or cylinder at the lockingend. The locking tube has an axis extending parallel to that of theligature itself and is positioned in an offset relationship to the stripcomprising the ligature. The locking tube has a locking taper at one endof thereof which engages the locking teeth of the insertion end of theligature to prevent disengagement of the ligature after installation.The locking tube is adapted for positioning within the tie slot of anorthodontic bracket which is advantageous in that it hides the lockingtube from view and also maximizes patient comfort.

In accordance with a second embodiment of the invention, a ligature isformed from nylon or other, similar materials and comprises an elongatestrip having locking teeth at both ends thereof. The locking teeth aretapered in the direction of the adjacent end of the ligature and havelocking surfaces facing in the opposite direction. The ends of theligature are extended in opposite directions through a small diameterlocking tube. The locking teeth of the ligature engage one another andthe ends of the locking tube to secure the ligature in place. In a thirdembodiment of the invention, a ligature is also formed from nylon, orother, similar materials. Unlike the first and second embodiments, theligature of the second embodiment does not employ locking teeth butinstead has relatively small diameter ends. In use, the opposite ends ofthe ligature are extended in opposite directions through a lockingsleeve which is initially open and which is crushable under the actionof pliers, etc. to secure the ligature in place. Either conventional orspecially designed pliers may be utilized in the practice of the thirdembodiment of the invention.

BRIEF DESCRIPTION OF DRAWINGS

A more complete understanding to the present invention may be had byreference to the following Detailed Description when taken inconjunction with the accompanying Drawings, in which:

FIG. 1 is an end view of a typical orthodontic bracket;

FIG. 2 is an illustration of a prior art O-ring type ligature;

FIG. 3 is an illustration of the method ad apparatus for ligatingorthodontic appliances comprising a first embodiment of the presentinvention;

FIG. 4 is an illustration of the apparatus of FIG. 3;

FIG. 5 is an enlargement of part FIG. 4;

FIG. 6 is an illustration of the method of the present invention;

FIG. 7 is a further illustration of the method of the present invention;

FIG. 8 is an illustration of an apparatus useful in the installation ofthe apparatus of FIG. 3;

FIG. 9 is an illustration of the method and apparatus for ligatingorthodontic appliances comprising a second embodiment of the presentinvention;

FIG. 10 is an illustration of the apparatus of FIG. 9;

FIG. 11 is an enlargement of a portion of FIG. 9 further illustrationthe method and apparatus of the second embodiment of the invention;

FIG. 12 is an illustration of an orthodontic ligature comprising a thirdembodiment of the invention;

FIG. 13 is an illustration of a locking sleeve useful in the practice ofthe third embodiment of the invention; and

FIG. 14 is an illustration of a locking sleeve installation of FIG. 13.

DETAILED DESCRIPTION

Referring now to the Drawings, and in particular to FIG. 1 thereof,there is shown a typical orthodontic bracket 10. Those skilled in theart will appreciate the fact that the bracket 10 illustrated in FIG. 1is illustrative of dozens if not hundreds of bracket designs which havebeen and are in the practice of orthodontia. The bracket 10 includes abody 12 formed from stainless steel, various plastics, various ceramics,etc. An archwire receiving slot 14 is formed in the body 12 forreceiving an archwire 15 therethrough. Typically, the dimensions of theslot 14 and those of those of the archwire 15 received therein are veryclosely controlled.

A pair of the tie wings 16 extend outwardly on opposite sides from thearchwire slot 14. A pair of ligature receiving slots 18 are locatedbeneath the tie wings 16. A ligature 20 extends from one of the slots18, then over an archwire 15 positioned in the slot 14, then downwardlyand through the opposite slot 18, and then back and over the archwire,and then back into the original slot 18 at the point of beginning. Thus,ligature 20 functions to secure an archwire positioned in the slot 14 inengagement with the bracket 10.

FIG. 2 illustrates an injected molded construction 22 in which aplurality of plastic O-rings 24 are formed on opposite sides of a runner26. The plastic O-rings 24 are of the type that are frequently used asligatures in securing an archwire to an orthodontic bracket illustratedin FIG. 1. The construction and function of the O-rings 24 is furtherexplained in U.S. Patent No. 4,038,753, granted to Klein on Aug. 2,1997. U.S. Patent No. 4,217,686, granted to Dragan on Aug, 19, 1990,describes an appliance for installing the O-ring type ligaturesillustrated in FIG. 2.

FIG. 3 illustrates an orthodontic bracket 30 having an archwire 32extending therethrough. The particular bracket 30 illustrated in FIG. 3is a twin bracket. However, those skilled in the art will appreciate thefact that the present invention is equally applicable to all of thevarious types of orthodontic brackets which are currently in use andalso those which have been used previously.

The bracket 30 has an archwire slot 34 which receives the archwire 32and tie wings 36 extending in opposite directions form the slot 34. Aligature receiving groove 38 extends under each of the tie wings 36 forreceiving a ligature therethrough. FIG. 3 further illustrates anorthodontic ligature 40 incorporating a first embodiment of the presentinvention.

FIG. 4 further illustrates the orthodontic ligature 40. The ligature 40comprises an elongate, very slender member 42 formed from a materialwhich has sufficient tensile strength to withstand, for an extendedperiod of time, the forces which are utilized in the practice oforthodontia for the repositioning teeth. I n accordance with thepreferred embodiment of the invention, the ligature 40 is formed fromnylon, although other materials may be utilized in the practice of theinvention in accordance with the requirements of particular applicationsthereof. The use of nylon is preferred for several reasons. First, nylonhas sufficient tensile strength, even when employed in small diameterelongate members, to withstand forces of the type utilized in thepractice of orthodontia. Second, nylon neither absorbs water nor stainsnor discolors when utilized in the human mouth. Third, nylon may besupplied either in a highly translucent mode, or in any of a widevariety of colors as may be required by particular applications of theinvention. Fourth, nylon is a low-friction material as compared tomaterials that have heretofore been used in orthodontic ligatures.

The ligature 40 has an insertion end 44 and a locking end 46. Theinsertion end 44 is provided with a plurality of locking teeth 48 eachhaving a locking surface which faces from the insertion end 44. That is,each of the teeth 48 has a flat or blunt locking surface which facestoward the locking end 46 and away from the insertion end 44 of theligature 40.

Referring to FIG. 5, the locking end 46 of the ligature 40 is shown ingreater detail. The locking end 46 comprises a hollow/cylinder or tube50 adapted to receive the insertion end 44 therethrough. The tube 50 hasan axis which extends parallel to the axis of the ligature 40, Inactuality, the locking end 46 comprises a locking tube 50 which issecured to, positioned on, and extends parallel to the main portion ofthe ligature 40.

The locking end 46 of the ligature 49 comprising the locking tube 50 hasa locking taper 52 at the end thereof remote from the insertion end 44.The locking taper 52 functions to receive the insertion end 44 and thelocking teeth 48 therethrough while preventing reverse movement of theinsertion end 44 by engagement of the locking surface of each of thelocking teeth 48 with the locking taper 52. In this manner, the ligature40 may be drawn tight but cannot be disengaged short of being cut inorder to effect its release from the working position.

The method of and apparatus for orthodontic ligature comprising thepresent invention are further illustrated in FIGS. 3, 6, and 7.Referring first to FIG. 6, the insertion end 44 of the ligature 40 isinserted through the tube 50 comprising the locking end 46 of theligature 40, thereby forming a loop 54. Referring to FIG. 3, the loop 54is positioned in the ligature receiving slot 38 on one side of anorthodontic bracket 30 and is passed over the top of the archwire 32 andinto the ligature receiving groove 38 on the opposite slot of thebracket. Referring to FIG. 7, this may be accomplished by means of apair of tweezers 56 which engage the tube 50 which comprises the lockingend of the ligature 40. Next, a hemostat 58 is engaged with theinsertion end 44 of the ligature 40 and is utilized to draw theinsertion end 44 through the tube 50 comprising the locking end 46 ofthe ligature 40. As the insertion end 44 is drawn through the tube 50,the teeth 48 subsequently engage the locking taper 52. Pulling of theinsertion end 44 through the tube 50 continues until sufficient tensionhas been established in the ligature 40 to accomplish the requisiteorthodontic function as determined by the doctor utilizing the presentinvention.

It will be appreciated that the teeth 48 are tapered in the directionfacing the insertion end 44 of the ligature 40 while comprising lockingsurfaces facing the locking end 46. Therefore, as each successive tooth48 engages the locking taper 52 of the tube, the ligature 40 is retainedin such position and disengagement is prevented, After the requiredamount of tension has been established in the ligature 40 by drawing theinsertion end 44 through the tube 50, the portion of the insertion end44 of the ligature 40 extending beyond the tube 50 is removed utilizingcutters, etc., whereupon the ligature 40 remains in place and functionto secure the archwire 32 in the archwire slot 34 during the orthodonticprocedure. At any convenient time as may be determined by the installingorthodontist, the ligature 40 can be removed by simply cutting andconvenient portion thereof.

Referring particularly to FIG. 3, the tube 50 at the locking end 46 ofthe ligature 40 is preferably positioned within one of the ligaturereceiving grooves 38 of the bracket 30. By this means the tube 50 isblocked from view. Also, the tube 50 is prevented from causingdiscomfort for the patient since it is completely contained within theligature receiving groove 38.

Referring now to FIG. 8, there is shown an appliance 60 useful in thepractice of the invention. The ligature 40 of the present invention isextended through a slot 64 and out through an exit 66. A wheel 68provided with a suitable gear engages the locking teeth 48 of theligature 40.

A ratchet wheel 70 is secured to the wheel 68. A ratchet pin 72 isactuated by a handle 74 to effect actuation of the ratchet wheel andtherefore the wheel 68 to move the ligature 40 through the slot 64.Reverse movement of the ratchet wheel 70 and therefore the wheel 68 isprevented by an anti-reverse pin 76. The load applied to the ligature 40is controlled by a tension spring 78. After the required tension hasbeen established in the ligature 40, the handle 74 is moved furtherinwardly, thereby actuating a cutoff blade 80 to sever the portion ofthe ligature 40 extending beyond the tube 50 comprising the locking end46. FIGS. 9,10, and 11 illustrate a second embodiment of the invention.In accordance with the second embodiment, a ligature 90 is formed fromnylon or other, similar materials. The ligature 90 comprises a thin,elongate strip having sufficient tensile strength to withstand theforces that are common to orthodontia. The ligature 90 differs from theligature 40 of the first embodiment in that it is provided with lockingteeth 92 at both ends thereof. In each instance the locking teeth 92 aretapered in the direction of the adjacent end of the ligature 90 and havea locking surface facing in the opposite direction.

FIG. 11 further illustrates the methods and apparatus of the secondembodiment of the invention. The opposite ends of the ligature 90 areextended in opposite directions through a locking sleeve 94. The insidediameter of the locking sleeve 94 is closely controlled so that theopposite ends of the ligature 90 can be pulled therethrough withoutdifficulty while assuring that the locking surfaces of the locking teeth92 will engage one another and the end surfaces of the locking sleeve 94to assure that the ligature 90 will remain locked in place after thedesired tension has been applied thereto. FIGS. 12, 13, and 14illustrate a third embodiment of the invention. In accordance with thethird embodiment of the invention, a ligature 100 is formed from nylonor other, similar materials. The ligature 100 differs from the ligatures40 and 90 of the first and second embodiments, respectively, in that itis not provided with locking teeth. Instead, the ligature 100 hasrelatively small diameter portions 102 at each end thereof. FIG. 13illustrates a locking sleeve 104 useful in conjunction with the ligature100 in the practive of the third embodiment of the invention. Thelocking sleeve 104 is initially open to allow the ends of the ligature100 to be inserted therethrough in opposite directions. After thedesired amount of tension has been applied to the ligature 100, a plug106 is inserted into the locking sleeve 104, after which the lockingsleeve 104 is crushed to secure the plug 106 and the ligature 100 inplace. Alternatively, the plug 106 may be designed to snap lock into thesleeve 104 as shown.

The locking sleeve 104 may be crushed into the locked conditionutilizing conventional pliers. Alternatively, the tool 108 illustratedin FIG. 14 may be utilized in conjunction with the locking sleeve 104.The tool 108 is plier-like in construction and has specially designedtips 110 which engage the locking sleeve 104 to effect crushing thereofinto the locked position. If the snap lock plug alternative is used, thetool 108 is employed to retain the sleeve 104 as the plug 106 is snaplocked in place.

Although preferred embodiments of the invention hae been illustrated inthe accompanying Drawings and described in the foregoing DetailedDescription, it will be understood that the invention is not limited tothe embodiments disclosed, but is capable of numerous rearrangements,modifications, and variations of parts and elements without departingfrom the spirit of the invention.

What is claimed is:
 1. In an orthodontic system of the type comprisingan orthodontic brackett having an archwire slot, an orthodontic archwireextending through the archwire slot of the bracket, and a ligature forsecuring in the archwire slot, the improvement comprising: an elongate,thin ligature having a predetermined tensile strength sufficient towithstand orthodontic forces and having an insertion end and a lockingend; the ligature having locking members at the insertion end thereof; aligature locking member receiver mounted at the locking end of theligature and comprising a tubular ligature receiving passagewayextending parallel to the ligature; the locking members of the ligaturefor engagement with the ligature locking member receiver to secure theligature in engagement with an orthodontic bracket and an archiveextending therethrough.
 2. A ligature for securing an orthodonticbracket having an archwire slot to an orthodontic archwire extendingthrough the archwire slot of the bracket comprising: an elongate, thinligature having a predetermined tensile strength sufficient to withstandorthodontic forces and having opposite ends; the ligature having lockingmembers at one end thereof; a ligature locking member receivercomprising a tubular ligature receiving passageway extending parallel tothe ligature and located at the opposite end of the ligature from thelocking members; the locking members of the ligature for engagement withthe ligature locking member receiver to secure the ligature inengagement with the orthodontic bracket and the archwire.